A limo (town car) driver doesn't know how to find your specific address any better than a yellow cab driver. And they charge a lot more than a taxi. Last time I took a town car, from either LaGuardia or Newark (I forget which), it cost me around $80. The basic charge, plus tolls, plus tip.
I now take the bus from Port Authority to Newark Airport. It's about $16 one way and they let you off at your terminal. That's it. Takes about 25 minutes.
<-----I'M TOTES ROLLING MY EYES